Will the real Minmi please stand up?

Earlier the ankylosaurs, represented by Minmi, (Figs 1, 2) were phylogenetically and heretically separated from their putative Thyreophoran sisters, like Stegosaurus. A phylogenetic analysis nested the former with the basal orinithischian, Scelidosaurus, while nesting the latter with the more derived and much smaller ornithischian, Scutellosaurus. All prior studies presumed Scelidosaurus and Scutellosaurus were sisters in armor. In the large reptile tree the two armored clades of ornithischians developed their defenses by convergence.

Minmi paravertebrai (min-my, Molnar 1960, early Cretaceous, 3m, Fig. 2) ) is one of the most popular dinosaurs and very likely THE most popular ankylosaur. It’s small and Australian. It’s been an illustration, a sculpture, a toy, and a stamp––all in addition to its original role as a fossil (Fig. 1).

When I went searching for Minmi data
I found little consistency in Minmi reconstructions (Fig. 1). Many seem to be based on something other than the original fossil (Fig. 2). Some have a nodosaur-like skull. Some have legs that are too long. Others make up their own armor.

Figure 1. The many ways the Australian ankylosaur, Minmi, has been portrayed. Each one is different.

Figure 1. The many ways the Australian ankylosaur, Minmi, has been portrayed. Each one is different. The illustration in the lower right hand corner appears to most closely resemble the original fossil material.

That’s why
Minmi is shown here (Fig. 2) as a reconstruction, along with its original fossil and tracings. There should be a one-to-one correspondence of elements here. At least that was the intention. The distal tail is unknown and restored here.

Figbure 2. Minmi paravertebra as found, tracings in both dorsal and ventral aspect and reconstruction based on the tracings.

Figbure 2. Minmi paravertebra as found, tracings in both dorsal and ventral aspect and reconstruction based on the tracings. The skull is not heavily armored, so provides skull sutures, colorized here from hints provided by Molnar. 

Minmi paravertebra was recovered as the most basal anklylosaur by Thompson et al. 2011. Overall smaller than most ankylosaurs, the skull was larger, the torso shorter and the legs relatively longer than larger, later forms like Ankylosaurus and Euoplocephalus.

Distinct from the more basal Scelidosaurusthe torso of Minmi was wider than tall. The pubis was a vestige. The limbs were all subequal in length. The ilia rotated laterally so their medial surfaces became dorsal, acting like armor plates. Individual osteoderms were larger. No temporal fenestra appear on the skull as bone infilled all those cavities.

Interesting gut contents
consist of fragments of fibrous or vascular plant tissue, fruiting bodies, spherical seeds, and vesicular tissue (possibly from fern sporangia). The fragments are uniform in size and cut cleanly, indicating oral processing supported by inset teeth probably within cheeks.

References
Haubold H 1990. Ein neuer Dinosaurier (Ornithischia, Thyreophora) aus dem Unteren Jura des nördlichen Mitteleuropa. Revue de Paleobiologie 9(1):149-177. [In German]
Molnar RE 1980. An ankylosaur (Ornithischia: Reptilia) from the Lower Cretaceous of southern Queensland. Memoirs of the Queensland Museum 20:65-75
Thompson RS, Parish JC, Maidment SCR and Barret PM 2011. Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora). Journal of Systematic Palaeontology 301-312.

Minmi YouTube video here.

wiki/Minmi

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